前端两三问(20190915)

1、Js获取当前时间

function dateFormat(date, format) {
  if (!date) {
    return ''
  }
  if (!(date instanceof Date)) {
    date = new Date(date)
    if (date.toString() === 'Invalid Date') {
      return '无效时间戳'
    }
  }
  format = format || 'yyyy-MM-dd hh:mm:ss'
  const o = {
    "M+": date.getMonth() + 1, //月份
    "d+": date.getDate(), //日
    "h+": date.getHours(), //小时
    "m+": date.getMinutes(), //分
    "s+": date.getSeconds(), //秒
    "q+": Math.floor((date.getMonth() + 3) / 3), //季度
    "S": date.getMilliseconds() //毫秒
  };
  if (/(y+)/.test(format)) {
    format = format.replace(RegExp.$1, (date.getFullYear() + "").substr(4 - RegExp.$1.length));
  }
  for (const k in o)
    if (new RegExp("(" + k + ")").test(format)) {
      format = format.replace(RegExp.$1, (RegExp.$1.length === 1) ? (o[k]) : (("00" + o[k]).substr(("" + o[k]).length)));
    }
  return format;
}

console.log(date.Format(new Date(), 'yyyy-MM-dd')   // 2019-09-11

2、css 三角形

.sj {
  width: 0; 
  height: 0;
  border-width: 100px;
  border-style: solid;
}

.sj-left {
  border-color: transparent pink transparent transparent;
}

.sj-right {
  border-color: transparent transparent transparent pink;
}

.sj-top {
  border-color: transparent transparent pink transparent;
}

.sj-bottom {
  border-color: pink transparent transparent transparent;
}

3、js 取并集 交集

  let a = [1,2,3,4,5]
  let b = [2,4,6,8,10]

  let sa = new Set(a);
  let sb = new Set(b);

  // 交集
  let intersect = a.filter(x => sb.has(x));

  // 差集
  let minus = a.filter(x => !sb.has(x));

  // 补集
  let complement  = [...a.filter(x => !sb.has(x)), ...b.filter(x => !sa.has(x))];

  // 并集
  let unionSet = Array.from(new Set([...a, ...b]));

  console.log("a与b的交集：", intersect);
  console.log("a与b的差集：", minus);
  console.log("a与b的补集：", complement);
  console.log("a与b的并集：", unionSet);